MySQL之递归小问题
编程学习 2021-07-05 14:36www.dzhlxh.cn编程入门
这篇文章主要介绍了MySQL之递归小问题,需要的朋友可以参考下
mysql本身不支持递归语法，但可通过自连接变相实现一些简单的递归
--递归小方法：临时表和普通表的不同方法
--这题使用的是2次临时表查询父节点的递归
drop table if exists test;
create table test(
id varchar(100),
name varchar(20),
parentid varchar(100)
);
insert test select
'13ed38f1-3c24-dd81-492f-673686dff0f3', '大学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select
'1ce203ac-ee34-b902-6c10-c806f0f52876','小学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d' union all select
'37e2ea0a-1c31-3412-455a-5e60b8395f7d', '教师' , null union all select
'c877b7ea-4ed3-f472-9527-53e1618cb1dc', '高数老师', '13ed38f1-3c24-dd81-492f-673686dff0f3' union all select
'ce50a471-2955-00fa-2fb7-198f6b45b1bd', '中学教师', '37e2ea0a-1c31-3412-455a-5e60b8395f7d';
delimiter $$
create procedure usp_ser(in idd varchar(100))
begin
declare lev int;
set lev=1;
drop table if exists tmp1;
drop table if exists tmp2;
CREATE TEMPORARY TABLE tmp1(id varchar(100),name varchar(20),parentid varchar(100),levv int);
CREATE TEMPORARY TABLE tmp2(pid varchar(100));
insert tmp2 select parentid from test where id=idd;
insert tmp1 select t.* , lev from test t join tmp2 a on t.id=a.pid;
while exists(select 1 from tmp2 )
do
truncate tmp2;
set lev=lev+1;
insert tmp2 select t.id from test t join tmp1 a on t.id=a.parentid and a.levv=lev-1;
insert tmp1 select t.*,lev from test t join tmp2 a on t.id=a.pid;
end while ;
select id,name,parentid from tmp1;
end;
$$
delimiter ;
call usp_ser('c877b7ea-4ed3-f472-9527-53e1618cb1dc');
+--------------------------------------+----------+--------------------------------------+
| id | name | parentid |
+--------------------------------------+----------+--------------------------------------+
| 13ed38f1-3c24-dd81-492f-673686dff0f3 | 大学教师 | 37e2ea0a-1c31-3412-455a-5e60b8395f7d |
| 37e2ea0a-1c31-3412-455a-5e60b8395f7d | 教师 | NULL |
+--------------------------------------+----------+--------------------------------------+
call usp_ser('13ed38f1-3c24-dd81-492f-673686dff0f3');
+--------------------------------------+------+----------+
| id | name | parentid |
+--------------------------------------+------+----------+
| 37e2ea0a-1c31-3412-455a-5e60b8395f7d | 教师 | NULL |
+--------------------------------------+------+----------+
call usp_ser('37e2ea0a-1c31-3412-455a-5e60b8395f7d');
Empty set (0.02 sec)
上面的方法因为由于MySQL中不允许在同一语句中对临时表多次引用，所以用2次临时表
狼蚁网站SEO优化给个一次性用普通表完成的 查询子节点的递归查询
核心代码
drop table if exists test; create table test( id INT, parentid INT ); insert test select 1, 0 UNION ALL SELECT 2, 1 UNION ALL SELECT 3, 1 UNION ALL SELECT 4, 0 UNION ALL SELECT 5, 2 UNION ALL SELECT 6, 5 UNION ALL SELECT 7, 3 ; Go delimiter $$ create procedure usp_ser(in idd varchar(100)) begin declare lev int; set lev=1; drop table if exists tmp1; CREATE TABLE tmp1(id INT,parentid INT ,levv INT,ppath VARCHAR(1000)); INSERT tmp1 SELECT *,lev,id FROM test WHERE parentid=idd; while row_count()>0 do set lev=lev+1; insert tmp1 select t.*,lev,concat(a.ppath,t.id) from test t join tmp1 a on t.parentid=a.id AND levv=LEV-1; end while ; SELECT * FROM tmp1; end; $$ delimiter ; call usp_ser(0); /* +------+----------+------+-------+ | id | parentid | levv | ppath | +------+----------+------+-------+ | 1 | 0 | 1 | 1 | | 4 | 0 | 1 | 4 | | 2 | 1 | 2 | 12 | | 3 | 1 | 2 | 13 | | 5 | 2 | 3 | 125 | | 7 | 3 | 3 | 137 | | 6 | 5 | 4 | 1256 | +------+----------+------+-------+*/